In the conventional art, a switching power supply is often used to solve the problem of low conversion efficiency of the power system. However, the circuit topology of the switching power supply is complex, so that the integrated density can't be effectively improved. In order to minimize size and improve efficiency and application flexibility, the conventional power module has a leadframe to lead out the pin. The leadframe is used as the carrier of the integrated circuit chip, and the electrical connection between the output terminal of the chip and the outer leading wire is implemented by wire bonding. Consequently, the small terminal of the semiconductor chip is converted into the large-size output pin for facilitating the power module to assemble onto electronic devices or circuit boards.
Generally, the conventional lead frames are fabricated by means of precision stamping or etching, and integrated by leads and frames. The frame is a carrier to support the leads. When the lead is fixed with the chip or power module, the frame is cut off, and then the exposed portion of the lead is subjected to the necessary forming process to produce the pin as final shape. If the leadframe of the power module is used as the pin, the power density of the power module can be improved. However, the leading terminal of the leadframe can only be led out at the edge of the printed circuit board and the printed circuit board should have a trace for further conduction, so as to increase the trace load on the printed circuit board and the power loss. Furthermore, the leading terminal of the leadframe tends to be led out from the outside of the final forming module, and the package footprint of the module is increased. In addition, if the power module uses a leadframe to lead out the pin of the surface-mount technology (SMT), the final formation of the pin pad area is small, so that it is unfavourable to be applied by the customers and reduce the loss of solder joints. On the other hand, after the forming process of the leadframe, the frame part will be cut off and the material is wasted. Further due to the existence of the frame, the entire area of the leadframe is larger, and the cost is increased. When the power module having the leadframe is introduced to a molding process, the molding tools need to avoid the leadframe or match with the leadframe so as to form a sealed molding chamber. Thus, the complexity and the volume of the molding tools are increased, and the possibility of developing general molding tools is reduced.
In view of the foregoing problem, there is a power module having leading terminals, which are directly led out from the printed circuit board. Although the leading terminals of the power module can be arranged at any positions in the package of the power module, additional devices can't be arranged on the side of the printed circuit board with the lead-out terminals, so that the utilization of the printed circuit board will be reduced, the footprint of the module will increase, or the power loss will be increased because a detour-type routing is implemented to add other devices.
There are some power modules provided with plastic molding, the entire module with plastic molding has leading terminals implemented by means of vias and surface metallic coating similar to those of the printed circuit board. However, the surface metallic coating can't obtain a thick metal layer, and it will influence the efficiency while the power module is applied for a high current power conversion. At the same time, it is difficult to plate metal in the deep holes, so that it is difficult to lead out the leading terminals from the inner portion of the printed circuit board. Consequently, the leading terminals are led out from the edge of the printed circuit board with plastic molding, the traces of the printed circuit board are led to the edge, and then the trace load and the power loss are increased.
Although the requirements of the efficiency and the power density of power modules are increased, the prior power modules fail to provide a leading way to meet the requirements. Therefore, there is a need of providing a power module having a lead component and a manufacturing method thereof to overcome the above drawbacks.